North American Agroforestry. Группа авторов

Читать онлайн книгу.

North American Agroforestry - Группа авторов


Скачать книгу
found that tree‐based intercropping systems enhanced avian species diversity compared with old fields and monocropped areas. When a pasture is converted to agroforestry, birds normally associated with woodlands are being attracted to agroforestry and, along with birds normally found in open fields, create a unique assemblage of species. Mcadam, Sibbald, Teklehaimanot, and Eason (2007) examined the effect of temperate silvopastoral systems on certain invertebrate groups, including carabid beetles and spiders, and on the number of individuals and species of birds. They reported that the presence of trees on grasslands attracted invertebrates, which might have provided an enhanced food supply, which attracted birds. They concluded that, even at an early stage, silvopastoral systems had a positive impact on birds and could significantly enhance biodiversity.

Treatment Whole plant DW Root DW Shoot DW Root/shoot ratio
———————— g plant−1 ————————
2002
Non‐barrier 29.78 b (2.67) 13.53 c (0.43) 26.25 b (1.81) 0.12 c (0.02)
Barrier 54.04 a (3.76) 17.60 b (0.23) 46.44 a (2.54) 0.16 b (0.01)
Monoculture 57.33 a (3.71) 18.70 a (0.69) 48.63 a (3.07) 0.19 a (0.01)
2003
Non‐barrier 25.13 c (1.88) 12.83 c (0.21) 22.29 c (1.71) 0.13 c (0.01)
Barrier 50.76 b (3.85) 16.88 b (0.41) 43.88 b (3.56) 0.16 b (0.01)
Monoculture 72.60 a (5.71) 12.19 a (0.96) 60.40 a (4.95) 0.21 a (0.01)

      Note. In a given column for every growing season, means followed by a different letters are significantly different at α = 0.05. The standard error of the mean is given in parentheses.

      Competition for water

      Although belowground competition has been documented in many agroforestry systems, it is difficult to separate the belowground competition for water from that for nutrients. Competition for water, however, has been detected in some temperate agroforestry systems. In a silvopastoral study in the Canterbury region of New Zealand, Yanusa et al. (2005) reported a slightly lower water potential in radiata pine (Pinus radiata D. Don) trees planted in an alfalfa (Medicago sativa L.) pasture compared with trees growing in a vegetation‐free control treatment. Competition for water led to a 44% decrease in instantaneous CO2 assimilation, a 48% decrease in stomatal conductance, and a 64% decrease in growth between trees growing in the alfalfa pasture and trees growing in the alfalfa‐free control treatment (Yanusa et al., 2005). In a recent study in a temperate silvopasture system in Patagonia, Argentina, Quinteros, Bava, Bernal, Gobbi, and Defosse (2017) studied the competition effects of herbaceous vegetation on the survival, growth, and plant water relations of planted Nothofagus pumilio seedlings and observed higher survival and growth and better plant water status where competition from herbaceous vegetation was controlled, indicating strong interspecific competition otherwise.


Скачать книгу